1. Field of the Invention
The invention refers to a tri-axis close-loop feedback controlling module for electromagnetic lens driving device, which employs a 6-pin Hall element to allow the electromagnetic lens driving device to control the focusing operations of the auto-focus module along the Z-axis based on a control signal generated according to the X-and-Y axial positions of the auto-focus module, so as to achieve the functions of tri-axis close-loop feedback control.
2. Description of the Prior Art
Digital photography technology has been widely applied to most of the portable electronic devices such as the cellular phones. Various miniaturized techniques in the lens module are involved to make all these applications possible; in particular, the voice coil motor (VCM) technique. The VCM introduces a combination of coiled magnets and spring plates to drive a lens to move back and forth along a photo axis for image-capturing, so as to perform auto-zooming and/or auto-focusing of the lens module. Further, in this trend of demanding for devices capable of high-level photographing functions, photographic quality and various camera functions such as thousand pixels, anti-hand shake ability and so on are equipped to distinguish high-end camera from cost-down level. However, in an optical system composed of an optic lens module, such as a camera system or a video recorder system, hand shake or some external situations usually occur to alter optical path so as to degrade the imaging upon the image-compensation module and further to obscure the formation of the images. A conventional resort to resolve this problem is to introduce a further compensation mechanism for overcoming possible shaking during the imaging. Such a compensation mechanism can be either digital or optical. State of the art digital compensation mechanism is to analyze and process the digital imaging data capturing by the image-compensation module, so as to obtain a clearer digital image. Such a mechanism is also usually called as a digital image stabilization (DIS) mechanism. On the other hand, the optical compensation mechanism, usually called as an optical image stabilization (OIS) mechanism, is to add a shake-compensation module upon the lens module or the image-compensation module.
However, conventional technologies usually employ two different and yet independent control circuitries for the feedback circuits of the auto-focus module and the OIS module in the same camera device. That means, one control circuitry is used for receiving feedback signals of the auto-focus module and also controlling the auto-focus module based on the feedback signals, while another control circuitry is used for controlling the OIS module based on the feedback signals of the OIS module. More particularly, in the conventional technologies, a feedback circuit is individually furnished for detecting and generating a feedback signal according to the position and movement of the lens along its optical path (usually also called as the Z-axis), and thus the auto-focus module can control and drive the lens to move along the Z-axis according to the feedback signal so as to conduct auto-focusing operations; in the other hand, another feedback circuit is individually furnished for detecting and generating another feedback signal according to the position and movement of the lens along a horizontal plane perpendicular to the optical path (usually also called as the X-Y axial plane), and thus the OIS module can control and drive the lens to move along the X-Y axes according to said another feedback signal so as to conduct OIS operations. In the conventional technologies, the auto-focus module cannot receive any feedback signals from the OIS module when performing the Z-axial auto-focusing operations. However, when the OIS module is performing the OIS operations in order to compensate the biased position of the lens caused by shakings, the OIS module will move the X and Y axial positions of the lens, and thus the precise focusing position (Z-axial position) of the lens will also be changed accordingly. Which means, when the OIS module is performing the OIS operations, the auto-focus module is also required to perform and adjust its auto-focusing operations continuously. Unfortunately, because conventional technologies use two different and independent control and feedback circuits for the auto-focus module and OIS module to detect and control the movements of lens in the Z-axis and X-Y axes respectively, thus the responding and interacting speeds of the auto-focus module is relatively slower and delayed, which will cause delayed focusing operations when shakings occur. In addition, because the entire lens module (including lens and auto-focus module) is movable horizontally relative to the OIS module, the circuitry design is very difficult for conventional technologies if someone try to integrate the feedback circuit of the auto-focus module with the feedback circuit of the OIS module into one single circuitry.